Particles having surface properties and methods of making them

Details Particles having surface properties and methods of making them Particles having surface properties and methods of making them

1997-12-23

2001-12-11

Le, H. Thi (Department: 1773)

Stock material or miscellaneous articles

Coated or structually defined flake, particle, cell, strand,...

Particulate matter

C428S407000, C523S201000, C523S202000

Reexamination Certificate

active

06329057

ABSTRACT:

This invention relates to particles having surface properties and methods of making them.
It is concerned to provide surface properties on the particles that will cause them to be more firmly retained on substrates such as fabrics, vitreous surfaces or the skin. In the invention this is achieved by providing a polymer core to the particle with a surface of a different polymer.
These particles are particularly suitable for forming a stable-dispersion in a liquid concentrate containing active ingredient, such as a liquid detergent concentrate or liquid rinse conditioner containing a fragrance, wherein the active ingredient becomes imbibed or entrapped within the matrix of the polymer and this provides a product which is suitable for the controlled release of active ingredients.
SUMMARY OF THE PRIOR ART
Various polymer systems have been proposed as diluting systems for active ingredients. WO-A-90/08478 relates to food flavouring high note enhancement by micro-bead impregnated with flavoring containing volatiles and is protected by a soluble or swellable coating. This patent describes porous polymeric beads made from copolymers of divinylbenzene with styrene. The polymeric beads are preferably produced with a coating that retards the release of the flavouring. Illustrative coatings are hydroxyl propyl methyl cellulose and polyvinyl alcohol.
EP-A-297605 is directed to cell culture micro-carriers comprising (meth)acrylic ester polymer particles having positively charged groups on the surface. The polymer particles have an average diameter of between 100 and 1000 microns and are prepared by oil in water type suspension polymerisation of (meth) acrylic ester as a monomer followed by treating the resulting polymer particles with ammonia or amine having 5 or less carbon atoms. Typically polyvinyl alcohol may be used as a stabiliser in the aqueous phase of the polymer. The positive groups are generated by reacting the formed polymer particles with the amine or ammonia. In order for this to be possible it is necessary that the matrix monomer contains functional groups that react with the ammonia or amino compounds, e.g. glycydyl methacrylate.
JP-A-62289238 describes resistant anion exchangers. This patent describes an anionic exchange resin produced by polymerising glycydyl esters with other vinyl compounds and then reacting the polymer particles with ammonia or amines.
WO-A-92/18222 describes the preparation and use of solid non-porous crosslinked polymer beads. The beads are produced by first forming a monomer phase which comprises at least one monoethylenically unsaturated monomer and a monomer soluble initiator. The monomer phase is then combined with an aqueous liquid-phase which is substantially immiscible with the monomer phase to form a reaction mixture. An organic polymer colloid suspending agent can also be combined with the aqueous phase. Preferred suspending agents include polyvinyl polyols having a molecular weight of at least 40,000 and includes polyvinyl alcohol.
U.S. Pat. No. 4,842,761 discloses composite particles comprising a water soluble polymer and a water insoluble polymer. Discrete entities of one polymer are embedded within a matrix of the other polymer. The composite particles are used as perfume carriers in laundry detergents and provide controlled release perfume.
GB-A-2234901 describes a method of encapsulating a water insoluble substance, such as an insecticide, within a carrier capsule. The water insoluble substance is dissolved in a substance which is capable of modifying the carrier capsule so that it imbibes said substance and then entrapping said substance within the thereby modified carrier capsule by removal of the carrier capsule modifying agent. The patent exemplifies starch granules and cellulosic fibres as carrier capsule.
EP-A-285694 is one of a series of documents concerned with porous cross linked polymers obtained by polymerisation around droplets of a liquid substance which may subsequently be removed. These porous polymers can act as carriers for a variety of liquids. They are used in products for application to the skin, and give controlled release of the liquid to the skin.
THE INVENTION
We have now found that the properties of polymer particles—which are insoluble in water—for controlled retention and/or release systems can be improved by providing at the surface of the insoluble particles which are preferably formed from a (meth) acrylic monomer with at least three carbon atoms in the esterifying alcohol, a further polymer with free hydroxyl groups. Such polymer enhances deposition of the particles on substrates. The use of such particles can enhance deposition of perfume or other active ingredients.
The present invention may also provide particles containing an organic polymer core, which are insoluble in water, characterized in that the particles have at their exterior, a different polymer or polymers which provide(s) hydroxy functionality and cationic functionality. There may be a single such different polymer providing both those functionalities.
The cationic functionality may be provided by pendant cationic groups that have been derived from cationic vinyl addition monomer units bonded to the organic water insoluble polymer or cationic monomer units present in the further free hydroxy containing polymer.
The present invention also provides organic polymer particles of average particle size at least 40 microns, which have been produced by a process of suspension polymerization of organic water insoluble vinyl addition monomers in an aqueous medium comprising a hydroxy containing polymeric polymerization stabilizer that has free hydroxy groups, characterised in that a cationic monomer containing a C
4
-C
8
alkyl, aryl, alkaryl or aralkyl pendant groups are also present in the aqueous medium and this cationic monomer becomes incorporated onto the exterior of the polymer particles during the polymerization process.
The polymer particles of this invention are particularly suitable as carriers of active substances, especially those used in controlled release systems. The polymer particles can be dispersed into a liquid concentrate, such as a detergent concentrate or rinse conditioner containing an active ingredient such as a fragrance, so that the active ingredient is imbibed by the polymer particles and becomes entrapped within the polymer matrix. It is important that the particles remain in suspension in the active concentrate and do not agglomerate. The surface cationic character of the particles help stabilize the particles from agglomeration in the active concentrate, especially when such a liquid is an aqueous concentrated fabric conditioning agent.
Surprisingly it has been found that the presence of the functionalities at the exterior of the particles enhances the deposition of the particles onto certain substrates such as fabrics, skin etc. and thereby enhances the delivery of the active ingredient in a controlled fashion. An example of this could be a fabric treatment formulation that contains said particles, in which the active ingredient is an insecticide or insect repellant. The particles have a strong affinity for the fabric due to the hydroxy groups and possibly also by the cationic groups present at the exterior of the polymer particles. The polymer particles release insecticide for a prolonged period thereby preventing the damage to the fabric by insect grubs. The polymer particles also have the advantage of being easily removed from the substrate if required by normal laundering.
The hydrophobic monomer or monomer blend comprises a monoolefinic monomer such as (meth) acrylic esters optionally with other monomers such as styrene and optionally a polyolefinic monomer capable of crosslinking the hydrophobic monomer. In one preferred embodiment the hydrophobic monomer mixture comprises isobutyl methacrylate with 2 mole % divinyl benzene.
The cationic vinyl addition monomer is typically a vinyl addition compound that incorporates a quaternary ammonium group and contains a C
4
-C
8
alkyl, aryl, aralkyl or alkaryl pendant group

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